1. Field of the Invention
The present invention relates to an image forming apparatus such as an electrophotographic copying machine and a printer.
2. Description of the Prior Art
In such image forming apparatuses, when the power is turned on, the photoreceptor drum is rotated and the drum surface is charged by a main charger, and an automatic voltage control is performed to regulate the voltage applied to the main charger so that the surface voltage sensed by a surface voltage sensor is a predetermined surface voltage. The automatic voltage control is performed only when the power is turned on.
In a new image forming apparatus, if the environmental temperature is high, the sensitivity of the drum varies with an increase in the number of image formations. For this reason, if the voltage control is performed only at the power-on, the surface voltage becomes insufficient as the number of image formations increases, so that the image becomes pale.